Clasps and Levers Flashcards
1
Q
three components of a clasp assembly
A
- rest
- retainer (retention)
- bracer
2
Q
Type I clasp aka
A
suprabulge (above height of contour)
3
Q
Type II clasp aka
A
infrabulge
4
Q
Describe type I clasp
- origin
- retention
A
Occlusal in origin and FROM MINOR CONNECTOR
CROSSES BULGE (height of contour) and is ONLY RETENTIVE IN THE TERMINAL 1/3
retention can be on either the buccal or the lingual but NEVER BOTH
- so only one undercut per tooth
5
Q
examples of type I clasps
A
- circumferential - āCā clasp
- combination - combo
- ring
- embrasure
6
Q
retention and material for C (akers) clasp
A
Retention may be buccal OR lingual
Retention may be mesial OR distal
Material may be cast or wrought
- may be on framework or soldered on
7
Q
material for C clasp
A
Casting = tapered
- stronger and thick and ONE-PIECE CASTING
Wrought wire = round
- wire arm soldered or welded to frame work
8
Q
what do wrought wire clasps require?
A
requires soldering or welding which requires access to an open proximal surface
- bulky solder joints
9
Q
wire claps cannot originate from where?
A
Embrassures
10
Q
T/F Combo clasps can be used in areas with large cervical convergences and undercuts?
A
TRUE
- clasp we would use here
11
Q
material to make combo clasp?
A
Cast and wrought wire
- it is a C with a WIRE RETENTIVE ARM
- must be soldered or welded to casting
12
Q
origin of combo clasp
A
EDENTULOUS space
13
Q
flexibility of combo clasp
A
3 times MORE flexible than cast claps
14
Q
which is more subject to breakage, combo or cast clasp?
A
Combo
15
Q
protection in combo clasp?
A
Protects tooth AT ITS OWN EXPENSE
16
Q
Use of a ring clasp?
A
used on lone -standing MOLARS
used ONLY in non-rotating partials
17
Q
characteristics of a ring clasp
A
- 2 rests
- 2 minor connectors
- has almost continous contact on the tooth
- helps INCREASE BRACING ā continuous bracing arm
18
Q
what are disadvantages to embrasure clasps?
A
- lack guide planes
- places clasps too close together
- may act as an interproximal wedge
- may cause occlusal or esthetic problems
19
Q
what determines a clasp flexibility
A
- material
- length
- thickness
- straightness
- cross-sectional shape
20
Q
clasp flexibility: material
A
Cr-Co < Au (gold) < wire
- wire is most flexible
21
Q
clasp flexibility: length
A
short < long
short is less flexible
6mm minimum
22
Q
clasp flexibility: thickness
A
tip should taper
23
Q
clasp flexibility: staightness
A
bends decrease flexibility
should contain less bends as possible
24
Q
clasp flexibility: cross - sectional shape
A
flat < round
flat is less flexible than round
25
shape of cast clasp
1/2 round
COMBO = wrought - ROUND
26
what should the tip of a clasp always be?
tapered and should be trimmed and polished to shape after casting
*not paddle shaped
27
origin and finish of type 1 clasp
occlusal in origin --> from minor connector-->crossed bulge --. and retentive last 1/3 of it ends in the undercut
retention can be on the buccal or lingual aspect
28
in type 1 clasp retention arm called retention arm but in type II what are they called?
APPROACH arm (vertical)
Retainer (horizontal)
29
origin of type II clasp
gingival
30
where does type II clasp come from
gingival and FROM MESHWORK (not minor connector like type 1 clasp)
31
type II clasp location in reference to the bulge
stays below the bulge
| - so all of it is considered retentive
32
where is the retention on a type II clasp?
ALWAYS ON THE BUCCAL
33
Examples of type II clasps
1. Bar
2. T- bar
3. RPI
34
when you have an approach arm that means you must have what?
an approach arm
35
describe a bar (roach or J bar) clasp
this is a type 2 clasp
retention : DISTO-BUCCAL ONLY
36
which contacts less tooth surface? C clasp or Bar?
Bar
37
when is bar contraindicated
when an approach arm is contraindicated
38
T- bar clasp description
major difference is that the mesial aspect of the retentive part is above the survey line meaning it is NOT RETENTIVE BUT BRACING
- utilized when we do not have enough bracing on the opposite side of the tooth
*retention is still DB only
39
what does RPI stand for? what type of clasp?
R- Rest
P -Proximal plate
I - bar
type II clasp
40
RPI metal touching teeth?
less than a T and less than a bar clasp
41
retention on RPI
mid or mesial buccal only
42
rest in RPI for pre-molars?
| for cuspids?
pre-molars on mesio-occlusal
on cuspids = on mesio-lingual
43
bracing for RPI
2 minor connectors only and has least amount of metal when compared to any other clasp
44
minimum distance for any type 2 clasp?
2 mm from the free gingival margin for any undercut
3mm in height before it starts to swing back and join the framework
45
orientation of the approach arm to the free gingival margin in an RPI?
the approach arm is perpendicular to the free gingival margin
46
where you can use approach arms?
Can:
tooth = tissue (ideally) (.01 undercut) and tissue is 3mm below)
TISSUE UNDERCUT below 3mm - so goes into undercut after you alwready have the 3mm you need
ledge - okay again if you have 3mm and then it ledges out (we can contour the approach arm to the ledge)
47
where/ when are approach arms contra-indicated?
1. tissue undercut above 3mm (do not have the 3mm distance we need) tissue immediately goes into undercut
2. SEVERE TILT - if we try to adjust tooth - prepping too much
- way too much space between arm and tooth
48
implication of a space between tissue and approach arm?
it will become a food trap and cause lip irritation
49
amount of tissue that needs to be surveyed for a type II clasp?
3 mm
50
how to reduce a tissue ndercut?
tail down A/P tilt or laterally tilting it away
enamoloplasty
51
five incorrect uses for aproach arms?
1. double arms
2. skipping of teeth
3. lingual or palatal
4. reverse or distal (not going to swing an approach arm from an anterior tooth back)
5. molars (for same reasons) -- buccal shelf and zygomatic arch are there
* these are saying you do NOT USE THEM HERE
52
why would approach arm be contraindicated in molars?
because of location of buccal shelf and zygomatic arch
53
bracing aka
reciprocal
54
if she says 'what is reciprocal' she means what?
what is bracing
55
effect of pushing a fixed object
it will TIP unless something opposes it
56
three types of bracers
1. bracing ARMS
2. bracing BLANKETS (CONGULUM REST)
3. bracing MINOR CONNECTORS
57
cingulum rest can also be referred to as what
blanket
58
advantage of using 2 minor connectors with a type 2 clasp?
least amount of metal touches the teeth from the lingual aspect
59
if there is a C clasp of canine/ cuspid what is the bracer?
Lingual BLANKET -- but ONLY IN A NON-ROTATING PARTIAL
60
when do you use an arm for bracing and where
Molar or pre-molar only on buccal or lingual
61
when do you use 2 minor connectors and where
lingual of pre-molar or cuspid ONLY for type two claps
62
why can you not use 2 minor connectors on molars?
molars are TOO WIDE to be braced by 2 minor connectors
63
what type of bracing is used on canines of non-rotating partials?
BLANKET
64
major purpose of bracer
neutralize the effect of the retentive tip (so opposite of the retention aspect of clasp)
65
location of a bracer
must be MORE THAN 180 degrees from retentive tip
**directly opposite from the retainer
must be viewed from the OCCLUSAL and PROXIMAL
- At or slightly above the survey line because the retainer is below the survery line (hence the retention component of retainer)
66
Occlusal forces come from what?
rests
67
Lateral forces come from what?
clasps
68
clasps are placed where? why?
placed as gingivally as possible to reduce rotational or tipping forces
69
how do you lower survey line?
disk non-parallel to the path
70
two types of retentive undercuts
1. bilateral
| 2. diametric opposition
71
bilateral opposition undercut location
all undercuts are on buccal or all undercuts are on the lingual
72
diametric opposition
there are undercuts on the lingual and on the buccal within same arch (maxilla or mandible)
73
ideal location of ubndercuts
all (bilateral opposition) on the buccal aspect so all stress on the framework is directed outwards
74
if all undercuts on lingual implication?
the stress on the frame is all directed inwards
75
if have B + L mix of undercuts?
stress on framework is directed sideways
76
mandibular molars typically tilt which way?
lingually
77
implication of a longer edentoulous space?
greater the potential of a lever action on the abutment teeth
78
definition of class I lever
the FULCRUM is placed BETWEEN the effort and the load
| most common lever configuration
79
movement of load in effort in a class I lever
the movement of the load is in the OPPOSITE direction of the movement of the effort
80
Class 2 lever defintion
has the LOAD BETWEEN the effort and the fulcrum
81
movement of load and effort in class 2 lever
the movement of the load is in the SAME DIRECTION as that of the effort
82
location of fulcrum determines what
the lever
83
during rotation clasps act as?
Levers
84
the rest determines what for levers?
the CLASS of lever
85
implication of a longer lever arm?
more torque on abutment tooth -- easier to dislodge (not good)
86
rest seat on the distal? implication in terms of levers?
1st class
87
rest seat on the mesial? implication in terms of levers?
2nd class lever
88
fulcrum is?
the rest
89
effort is the?
biting
90
resistance is the?
tooth
91
clasp tip movement in a 2nd class lever?
down and away from effort (biting)
92
clasp tip movement in a 1st class lever? implication?
up
- bite down and clasp tip moves up into the undercut
CAN EXTRACT TEETH
93
a rest closest to the rotation is what type lever?
class 1 lever
94
rest away from the axis of rotation is what type of lever?
class 2 lever
95
if have two rests on the teeth what class lever?
THE REST CLOSEST TO THE ROTATION = THE LEVER
you classify lever based on which one is closest to the axis of rotation so could still be class I
96
Rest on cuspid in a rotating partial?
MESIAL LINGUAL
| cingulum/ blanket would include distal and would create a class 1 lever which we do not want
97
movement of a non- rotating partial?
up and down
| do NOT act as levers
98
movement of a rotating partial?
move anterio-posterior
| act as levers
99
ideal design for RPI clasp
short occlusal rest, short distal guide plane (occlusal 1/3) and mesial shifted I bar
100
biting force
36 psi
101
non rotating partials look like?
all edentulous spaces have TEETH AT EITHER END
102
all rotating partials have?
at least one edentulous space has soft tissue (no teeth) at one end
AKA distal extension
103
in non rotating partials describe what happens to the clasp in terms of active or passive?
when in place - passive
when lifted out of place = active (crosses survey line)
then becomes passive as it is past above survey line
then goes active to seat again
then once seated = becomes passive again
104
first and second choice of clasp for non-rotating partials?
1. C clasp (simplest design)
| 2. any - b/c all non rotating alike
105
what happens if clasp tip is mesial to the rest?
the lever changes to a class I
so dont go past the mesial line angle
on cuspids and pre molars always stay mid buccal or just slightly mesial to this
106
only way an RPA can protect a tooth?
if used with a class 2 lever
107
order of clasp choice in rotating partial?
1. RPI
2. RPA COMBO
3. Bar w/ 2nd class lever
4. RPA cast
108
cast contact vs wire contact
cast --> surface contact
wire --> point contact
109
if teeth are week how do you design?
treat as a DE with RPI
110
if bone is week how do you treat?
treat as DE with combo
111
implication of having a lingual bracing arm with class i lever
when lift up the arm will torque the tooth because it goes into survey line
112
if use two minor connectors for bracing how does this help?
now there are two minor connectors and they rotate around the tooth
bite down -- rest goes up and other slips into the gingival 1/3
lift up -- guide plane and rest engage then other part will slide up
no metal on the lingual portion of the tooth
113
RPA combo location of rest and tip
MO rest
| MB tip
114
RPI rest and tip location
MO rest
| Mid B tip
115
Bar rest and tip location
MO rest
| DB tip
116
RPA c rest and tip location
MO rest
| MB tip
